Design and calibration of an aberration–corrected crossed Czerny–Turner spectrometer system

Crossed Czerny–Turner (C–T) spectrometers are limited by significant aberrations due to large off–axis angles in spherical mirrors. A method is proposed to effectively reduce aberrations in portable crossed C–T spectrometers. The method optimizes grating position for field curvature correction, uses the Shafer equation to reduce coma across a wide spectral range, and employs a cylindrical lens for astigmatism correction by adjusting its tilt and wedge angles. The method significantly improves imaging quality, reducing spot width by 93.3 %. Additionally, a wavelength calibration model for the crossed C–T spectrometer was developed. This model employs an optimization fitting algorithm based on a sine–constrained least squares to accurately correct the optical system parameters. It achieves a wavelength calibration accuracy of 0.01 nm and a spectral resolution better than 3212 over a 200 nm range. This performance meets the requirements for detecting weak light signals in applications such as Raman spectroscopy and laser–induced breakdown spectroscopy (LIBS).